The erosive characteristics of ridge and ditch under countour tillage are studied in purple soil. The results show that, comparing with conventional tillage(CK), the runoff of contour tillage (CT) is diminished, but the sediment is not. When there are not any cover (including vegetable cover) on soil, the sediment of CT is mainly physical clay coming from its ridge, but that of CK is similar to the particle distribution of its source soil and its coefficient of soil structure is decreased significantly. It suggests that cover on ridge of CT will play an important role in controlling erosion, and CK will led to soil degradation notably.